1. Field of the Invention
The present invention relates, generally, to a thermoplastic polyolefin (TPO) nanocomposite composition. Preferably, the TPO nanocomposite composition of the present invention has low specific gravity and superior gloss reducing effect and scratch resistance, and may preferably be used for light automobile parts, uncoated automobile exterior parts, or the like.
2. Description of Related Art
In general, thermoplastic polyolefin (TPO) materials, commonly used as automobile exterior parts, comprise polypropylene resin as matrix, rubber for improving impact resistance, and an inorganic filler for suitably enhancing rigidity. In addition, various additives for improving processability and compatibility are often included. Although talc has been preferred as the inorganic filler, alternative light materials have been featured in recent years in the automobile manufacture industry for the improvement of fuel efficiency and to avoid environmental pollution.
Conventionally, plastic exterior parts for automobiles were mostly coated before use, and thus, appearance quality was not considered since the resin was not directly exposed to the outside environment. Recently, however, as the elimination of surface coating of some automobile exterior parts is demanded with regard to price competitiveness and environment friendliness, superior appearance quality is suitably required for resins.
Nanoclay, an inorganic filler like talc, has a characteristic layered structure. Since the development of a completely exfoliated nylon/nanoclay composite by the Toyota Central R&D Labs in 1997, active research has been carried out to develop a new TPO material by dispersing nanoclay in polypropylene. Completely exfoliated nanoclay is very useful in reducing material weight because mechanical properties comparable to or better than those of a polypropylene/talc composite comprising dozens of wt % of talc can be attained only with an amount of several wt %. Korean Paten Publication No. 2009-086725 and Korean Patent No. 713,703, incorporated by reference in their entireties herein, disclose propylene resin compositions comprising nanoclay. However, it is not easy to satisfy the gloss and scratch resistance requirements of uncoated automobile exterior parts with a low content of nanoclay, and additional strengthening materials capable of reducing gloss and enhancing scratch resistance are suitably required.
Glass bubbles with a hollow structure are glass beads having a specific gravity of about 0.6 and a diameter of 30 μm. With not so large specific gravity as compared to polypropylene resin, the glass bubble provides a suitable gloss reducing effect caused by diffused reflection on the surface when dispersed in polyolefin. Further, due to its slipperiness, it can suitably improve scratch resistance of the polypropylene resin. U.S. Pat. Nos. 6,403,692 and 6,455,630 and Korean Patent No. 683,230, incorporated by reference in their entireties herein, disclose polypropylene resins comprising glass bubbles. However, there is a need in the art for the development of a method to introduce the glass bubbles for extrusion without being broken.
The above information disclosed in this the Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.